This invention relates generally to die pressing, and more particularly it relates to a preforming press having a rotary die disc or matrix cooled by a cooling device and including a plurality of die borings in which the molding material is compressed by counteracting punches or rams. A filling device for feeding a molding composition into the die is arranged at the edge of the die disc and includes a housing provided with a filling funnel and, within the housing, a filling vane wheel and a dosing vane wheel.
During the operation of the preforming press of the above-mentioned type, the molding material or composition and the pressing parts are subject to heating. The heating results from the fact that the individual particles of the pellet under process come into a frictional contact with one another and also the press warms up due to the movement of its component parts. Furthermore, a heating effect takes place due to the friction of the pressed pellet against the walls of the die and also during the discharge of the completed pellet from the die.
Conventional preforming presses are unsuitable for processing materials which become unstable when exposed to heating such as, for example, material which liquefy upon heating or become pasty or viscous and cannot be, therefore, processed at a normal room temperature since the temperature increases causes the sticking of the pellets and the discharge of a completed and compressed pellet from the die is not possible in a regular manner when the temperature of the press becomes too high. The known preforming presses, moreover, have the disadvantage that in the course of processing temperature sensitive substances such as vitamins or enzymes, a considerable loss of effectiveness of these substances takes place due to the effect of the increased temperature.
The processing of other temperature-sensitive substances such as, for example sapositories shaped for anal introduction, upon which they become dissolved by the heat of the human body, or other oil or fat-containing substances such as paraafin or cocoa or chocolate-containing materials, could not hitherto been processed in conventional preforming presses for reasons stated above. To preform such thermally unstable substances, it has been necessary to employ different processing methods such as casting for example. This processing method, however, is relatively complicated and consequently costly.
Attempts have already been made to process thermally unstable materials in preforming presses in which the die disc is cooled by a cooling device including channels arranged in the body of the die disc through which the cooling liquid or gaseous agent circulates.
Such prior-art cooling device arranged in the die disc, however, has the disadvantage that moisture precipitates in the range of the die borings and impairs the quality of the processes material. Namely, when the die disc is cooled more intensively, the moisture of the ambient air precipitates in the range of the punch and on the walls of the die.